Method of and means for gas-tight sealing of shafts



1,681,075 WIEGERT METHD F Mll MENS FOR GAS TIGHT SEALIHG 0F SHAFTS Filed may 22, 3.925

- @qm/W Patented Aug. 14, 1902.8.

UNITED STATESA RUDOLF HEINRICH WIEGERT, OF MAGDEBURG, GERMANY.

METHOD O1' AND IEANS FOR GAS-TIGHT SEALING OF SEAFTS.

Application led May 22, 1926, Serial No. 111,080, and in Sweden, April 8, 1924.

In machines operating with injurious ses which are gas-tightly enclosed, as, for instance, gas compressors, the use of stalling boxes for tight inlet of the driving draft is non-economical and diicult due to their power-consuming action and troublesome attendance. Such a stuliing box, when used, for instance, in a plant of small capacity, may consume up to 100% of the theoretic need of power and is, moreover, very dillicult to keep tight, apart from the renewal of the packing material which, as in cooling machines, always requires special knowledge. Attempts have been made to hermetically seal machines and have resulted in expensive electrical machines in which the movement of compression is obtained, for instance, by the provision of a short-circuit rotor enclosed inside a cap-shaped portion of the hermetically sealed machinery and operated through the wall'of said cap by a stator surrounding said cap. In such case very high losses are caused due to the production of eddy currents in the wall of the ca p and due also to a lowering of the power factor as well'as of the etliciencv as a result of the inl crease of the distance 'between the rotor and the stator (that is the air-gap). In addition, such an arrangement may only be used for direct electric drive by means of alternating current.

Certain other designs of machines comprising hermetically sealed receptacles are restricted to apparatus operating on a cycle as cooling machines). In such machines the compressor enclosed within one of the sealed, rotary receptacles, is driven by a counterweight, and the condenser as well as the generator rotates with its outside in contact with cooling water or sea-water, whereby high friction losses are caused. v n

An object of the present invention is to overcome the said diiculties inherent to well-known driving systems for gas-tightly enclosed machines.

Another object of the invention is to reduce the losses of the driving system as far as possible.

A still further object is to permit the use of any type of driving motor and any driving iiuid desired without intermediate means.

These and other objects will be obtained by balancing the pressure existing within the chamber, apparatus, or the like to be ke ttight, from outside by providing a receptac e around the shaft as it projects from the said chamber and filling said receptacle with a pressure medium the pressure of which is caused to always correspond to the pressure exlstlng in the chamber or the like to be kept tlght thereby preventing leakage from or to the said chamber.

The nature of the invention will be best understood from the following detailed description of its operation taken in connection with the accompanying drawing in which Fig. 1 is alongitudinal section of one' embodiment of the invention as applied to a cooling machine.

Fig. 2 is a longitudinal section of a modilied embodiment with certain parts removed.

Fig. 1 shows a cooling machine comprising a compressor adapted, when in operation, to draw a gaseous fluid by suction from the chamber 20 and deliver it into the chamber 3 where said compressor is housed. The driving shaft 2 oi said compressor projects through the wall of the chamber 3 and'extends outside said wall through a chamber 1. Said chamber 1 contains oil to a level above the shaft 2 and its bearings. The space above the oil level in the chamber/1 communicates with the chamber 3 through an oil overow pipe 21 terminating below the level of the shaft within the chamber 3.

Situated at the opposite side of the chamber 1 to the chamber 3 is a balancing receptacle 5 filled with oil, said receptacle surrounding the shaft 2, and outside said receptacle 5 the shaft 2 extends through an additional rexeptlacle Gnarmally filled with oil to a certain eve When the machinery is in operation, a,

small pump 7 housed in the receptacle 6 will pass oil through a pipe 8 from the receptacle 6 into the receptacle 5 to maintain in the latter a pressure equal to that existing in the chamber 1. Due to the fact that the pressures within 1 and 5 are equal, no leakage can take place from 1 to 5 or vice versa. The tight sealing between 1 and 5 may be made still more eiective by using a long bearing which ma be'hardened and ground, ifv desired, an by hardening and grinding the corresponding portion of the shaft. Furthermore, it is of advantagel to have the shaft with its bearings within the chamber 1 immersed in the oil. The higher specific gravity of the oil as well as its viscosity will insure a better sealing effect than what may be obtained by the use of gas contact at the shaft. The viscosity of the oil may be further increased b y water cooling. In operation, a completely tight sealing may be obtained at the inlet of the shaft by the system above described. The point of leakage is. so to say, moved one step outwardly from the receptacle to be kept tight, that is, to the entrance of the shaft from chamber 5 to chamlaxr (l. By using a long and carefully worked bearing the leakage may be reduced at this point to an amount that may be readily balanced by the capacity of the small pump 7. The capacity of the pump 7 may, preferably. be about twice as large as the leakage.

Due to the fact that all stuing box friction is avoided and the pressure balancing lnedium consists of oil that will cause a reduction of the frictional losses in the bearings to the lowest amount possible (the oil pressure will balance the shaft so as to lift it from the bearing between the chambers 5 and (l) an ideal mechanical etlicicncy may be obtained by the system described. The loss ot' work iu the pump 7, whose piston dialneter may be something about 5-8 mm., is negligible.

lt may appear that if the pressure on the `shal't 2 is the same in all directions, said shaft cannot be lifted from its bearings. However, the pressure on the shaft 2 is the same only at the bearing between 9 and 5, while in the chamber 5 a different pressure prevails, for instance, 3 to 6 atm., prevails in G. Because of the pressure difference between rooms 5 and G the oil will be pressed around the shaft 2 outwardly from 5 to 6. This oil current holds the shaft 2 out of contact with the bearing metal, in practice, the bearing between 5 and G is considerably longer than that between 9 and 5 and consequently the former bearing has the greater iniiuence on the journaling of the shaft. Because of the friction in the bearing between 5 and G heilig considerably reduced, an ideal mechanical efficiency is obtained. Experiments have shown that the machine has an efficiency of 25 per cent greater than that of a machine provided with solid packing material.

lVith the machinery at rest the pump 7 will no longer balance the pressure within the receptacle 5. Now, the advantage of mounting the shaft frictionless, that is, without stutiing box and free from any hindrance against a smaller axial displacement thereof, will appear. Due to the difference in pressure existing between the main receptacle 1 the. chamber 5, which is different from the at- ,iconstitute the "31m Smm' mospheric pressure that prevails in the room,

and the atmosphere into which the shaft 2 projects, said shaft will be pressed with the power d against the hardened, and carefully ground end surface of the bearing, as at 9, and will thus act as a. nonreturn valve. This requires the provision of a movable clutch, as 10, between the driving shaft 2 to be sealed and the shaft of the compressor and, if desired, also between the driving engine, not shown, and said driving shaft 2.

It is a characterizing feature of the present invention that the shaft 2 or a part there of is movable against the seat at 9 and hence when the flange 9 is stationary with respect to the shaft 2, the shaft 2 must be movable not only at the clutch 10 between the shaft 2 and the compressor shaft but also between the said shaft 2 and the clutch of a driving motor. The shaft 2 in practice is partially fixed and movably connected with the flange 9 as for instance by means of a movable sleeve.

With the invention applied to electrically driven compressors or the like a hand-wheel 11 may be connected to the electrical contact and to the cooling water cock or valve in such a way as to enable control of the machine with all its auxiliary devices by a single manipulation. The hand-wheel 11 is also for the purpose of insuring the above said action of the shaft as a valve, inasmuch as it will cause a longitudinal displacement of the shaft when rotated. The system may then be operated as a usual stop valve in which case the shaft may be considered to In starting the machine the hand wheel 11 is operated to release the pressure against 9 exerted by the hand-wheel and, at the same time, operate the contact and the cooling water valve. (In stopping the machine, the said operations will take place in the reverse order.)

In order to adjust the pressure within the receptacle 6 the following provision is made. Extending between the top of the receptacle and the top of the receptacle is a connection 15. Said connection is controlled by a needle valve 16 which is in turn controlled by the pressure existing in the air space of the receptacle 1 through the intermedium of a diaphragm 17 subjected to said pressure, said diaphragm being connected to the stem of said needle Valve.

The operation of this regulating device is as follows:

With the pressures inside the chambers 1 and 3 at equal height the diaphragm 17 will be about its central position so as to keep the control valve 16 slightly open. Assuming the pressure in 1 exceeds that in 5, the diaphragm will be forced outwardly so as to lllf) close the valve 16 more before orcomletely. This will resultin a throttling'efect in the pressure conduit 8-5-15 of the small pump 7 thereby causing an increase of the pressure in the receptacle 5. If the pressure in the receptacle 5 exceeds that inthe chamber 1 then the diaphragm 17 will be pressed towards the chamber 1 so as to open the valve 16 thereby causing a reduction of the resistance inside the pressure 'conduit 8--5-15 of the small pump 7, the pressure in thereceptacle 5 sinking at the same time.

en usin a constant pressure in the chamber 1 the iaphragm and its valve may be replaced by a usual safety valve in connection with the receptacle 5. Invsubstitution for oil in the receptacles 5 andA 6 any other liquid desired may be used. The pump 7 may be replaced by an air compressor, a vacuum pump, a pressure receptacle, or the like.

In 2 I have shown a ily-weight 12 as carried y the shaft 2 within the receptacle 5. Said weight is used as an equivalence of the hand-wheel 11v in Fig. 1, inasmuch as it may be formed with inner threads engaging corresponding threads formed in the shaft. Said fly-weight due to its inertia will be somewhat marginal in its action inasmuch as it is slow to start when the lrotation of the shaft is initiated and will continue to rotate a little, after the rotation of the shaft is stopped, thereby causing a relative displacement of the shaft in the one dic rection or the other. In stopping the machinery the weight 12 is thus caused due to its inertia to turn on the threads of the shaft towards the hub 13 so as to abut against the end thereof and be pressed thereagainst at the same time increasing the pressure as exerted on the surface 9 by the shoulder 14 of the shaft. In starting, the inertia of the weight 12 and the sliding friction at the end of the hub 13 will cause the weight 12 to re lease from the end of the hub 13 thereby releasin the shaft.

Wit the interior of the rece tacle 1 subjected to a vacuum the shoul er 14 of the shaft may, for instance, be desi ed to coo erate with the hub 13 within e recepta e 5. The hand-,wheel 11 or the weight in such case be modified accordingly.

What I claim is:

1. A sealing device without solid packing material for ar rotating shaft projecting through the wallof a gas tight chamber, comprising a closed receptacle surrounding the shaft at the point where it projects through the chamber and adapted to contain a pressure medium, means for supplying the medium to the receptacle from a source other than the chamber, automatic means for re lating the pressure of the medium in per ect conformity to the pressure existing within said chamber and a valve in connection with said shaft and adapted to be controlled by. the last named pressure.

2. A. sealing device for a rotating shaft projecting through the wall of a gas tight chamber comprising a closed receptacle surrounding the shaft at the point where it projects through the wall and adapted to contain a pressure medium, means for supplying the medium to the receptacle from a source other than the chamber, automatic means adapted to regulate the pressure of themedium to conform'with the pressure existing within the chamber, means for permitting a slight axial movement of said shaft and a valve in connection with said shaft and adapted tobear against the wall.

3. `A. sealin device for a rotating shaft that rojects trough the wall of a gas tight cham er, comprisinga' receptacle surrounding said shaft at `the point Where it projects through said wall and adapted to contain ay pressure medium, means for supplying the` medium to the receptacle from a source other than the chamber, automatic means adapted to regulate the pressure of said medium to conform to the pressure existing Within the chamber and comprisinga membrane actuated on one side b the ressure in the chamber and on the ot 1er si e by the pressure in the receptacle and a regulating valve actuated by said membrane.

In testimony whereof I have signed my' name. Y

RUDOLF HEINRICH WIEGERT.

12 may l50 

